Force and Laws of Motion | Class 9 | Physics
Concepts
Newton’s First Law (Law of Inertia):
- An object will remain at rest or in uniform motion in a straight line unless acted upon by an external force. This law is often referred to as the “law of inertia.”
Newton’s Second Law (Law of Acceleration):
- The acceleration of an object is directly proportional to the net force acting on the object and inversely proportional to its mass. This can be represented by the equation: ( F = ma ), where ( F ) is the net force, ( m ) is the mass, and ( a ) is the acceleration.
Newton’s Third Law (Action and Reaction):
- For every action, there is an equal and opposite reaction. This means that if one object exerts a force on a second object, the second object exerts a force of equal magnitude and in the opposite direction on the first object.
Basic terms, definitions, formulas, and units related to Newton’s three laws of motion:
| Term | Definition | Unit |
|---|---|---|
| Newton’s 1st Law (Inertia) | An object will remain at rest or in uniform motion unless acted upon by an external force. | – |
| Newton’s 2nd Law | The rate of change of momentum of a body is directly proportional to the force applied on it. | Newton (N) |
| Newton’s 3rd Law | Every action has an equal and opposite reaction. | – |
| Mass | Amount of matter in an object. | Kilogram (kg) |
| Acceleration | Rate of change of velocity of an object. | m/s² |
| Force | A push or pull on an object due to an interaction. | Newton (N) |
| Momentum | The product of the mass and velocity of an object. | kg.m/s |
| Weight | The gravitational force acting on an object with mass. | Newton (N) |
| Friction | A force that opposes the relative motion between two bodies in contact. | Newton (N) |
| Normal Force | Perpendicular force exerted by a surface on an object in contact with it. | Newton (N) |
| Tension | A force transmitted through a string, rope, cable, or wire when it is pulled tight by forces acting from opposite ends. | Newton (N) |
Momentum
.
Recoil of a Gun
